An automatic transaction apparatus such as an ATM or a ticket vending machine is provided with a differentiation unit for differentiating the authenticity of bank notes, and this differentiation unit includes an optical sensor for capturing an image of a bank note being transported. This optical sensor includes a line sensor, and a linear light source for illuminating a bank note.
Paragraph [0003] of Patent Literature 1 describes that, since a genuine bank note and a color copied counterfeit note have different wavelengths of light transmitting through them, a light source with a plurality of wavelengths is used. Further, FIG. 15 and paragraph [0022] of Patent Literature 1 describe an identification sensor, constituting a light projection unit on an upper part by ultraviolet light, infrared light, and green light LEDs, and a light guide plate, and constituting a light transmission-reception unit on a lower part by infrared light, green light, and blue light LEDs, a photodiode array, and a light guide plate. Further, FIG. 16 and paragraph [0022] describe an example, constituting a light projection unit on an upper part by infrared light, green light, and ultraviolet light LEDs, and a light guide plate, and constituting a light transmission-reception unit on a lower part by infrared light, green light, blue light, and ultraviolet light LEDs, a photodiode array, and a light guide plate.
In particular, the ultraviolet light LED (LED array) of the light projection unit on the upper part described in FIG. 16 is arranged so as to irradiate the photodiode array via a bank note, and so does not directly irradiate the visible light LEDs. Further, since the visible light LEDs of the light transmission-reception unit on the lower part irradiate a bank note, the ultraviolet light LED (LED array) is configured so as to irradiate a bank note via a second light guide plate, and to additionally irradiate the rear surface side of the visible light LEDs. Accordingly, the visible light LEDs of the light transmission-reception unit on the lower part are not configured so as to directly irradiate the visible light LEDs.